Identification of Story Stiffness of Shear Buildings under Ambient Vibration Tests with Highly Noise polluted Data

In recent years, Vibration Based System Identification (VBSI) as a powerful tool to disclosure a mathematical expression of dynamic behaviors of structures, is taken into consideration for structure engineers. Among developed strategies for VBSI, the strategies identifying under ambient vibration tests without using input data, with no limitation in serviceability and no need to complex excitation tools, have been more desirable. In some cases, regarding to high numbers of Degrees Of Freedom (DOFs) and impossibility of recording in whole DOFs, it is necessary to identify physical characteristics beside modal parameters with recording in limited numbers of DOFs. Among those physical characteristics, stiffness parameter is more important. The main goal of this paper is to present a method for identification of story stiffness in shear type buildings using incomplete structural responses. At the first, the sub matrix of structural stiffness matrix is identified by the proposed method based on the structural dynamics theory and the realization theory-based Stochastic Subspace Identification (SSI) method and then story stiffness will be available. Since the presence of noise is imaginable in ambient vibration tests, effects of noise also been investigated. To evaluate the proposed method, a five-story analytical shear building is studied. Extensive analysis show the high ability and accuracy of proposed method in correct identification of story stiffness from incomplete output records even in presence of noise.